The present invention relates to a method for producing a multilayer substrate and a desmearing method.
Upon manufacture of a multilayer circuit board, permanganate treatment or other roughening treatment (e.g., desmear etching) is commonly used to develop the adhesion to interconnects while removing resin residues on the bottom of via holes.
However, when metal etching processes such as a subtractive process and a semi-additive process are applied for miniaturization of interconnects, the adhesion of the interconnects is reduced and metal residues catching on the roughened surface between the interconnects are difficult to remove and therefore overetching is more likely to occur during etching, making it difficult to form fine metal interconnects. Roughening under the interconnects is thus considerably disadvantageous.
Then, methods for removing resin residues remaining in via holes using plasma etching as another desmear treatment have been proposed (JP 2008-277717 A and JP 2002-50603 A).